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Lição 40 — Workshop: Integral e Síntese de Cálculo 1

Workshop final de Cálculo 1: exercícios integradores cobrindo somas de Riemann, TFC, substituição, área, volume, comprimento de arco e aplicações físicas da integral.

Used in: Cálculo 1 — Unidade 4 · USP MAC0105 · ITA MA-011

abf(x)dx=F(b)F(a)ddxaxf(t)dt=f(x)\int_a^b f(x)\,dx = F(b) - F(a) \qquad \frac{d}{dx}\int_a^x f(t)\,dt = f(x)
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Rigorous notation, full derivation, hypotheses

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Exercícios

Exercise list

33 exercises · 8 with worked solution (25%)

Application 21Understanding 8Modeling 2Challenge 2
  1. Ex. 40.1Understanding

    Expresse o limite como integral definida sobre o intervalo indicado:

    limni=1nxiΔxsobre [1,3]\lim_{n\to\infty}\sum_{i=1}^n x_i^*\,\Delta x \quad \text{sobre } [1,3]
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    A soma de Riemann limni=1nxiΔx\lim_{n\to\infty}\sum_{i=1}^n x_i^*\Delta x sobre [1,3][1,3] converge para a integral definida 13xdx\int_1^3 x\,dx.
  2. Ex. 40.2Application

    Expresse o limite como integral definida identificando o intervalo correto:

    Rn=1ni=1ninR_n = \frac{1}{n}\sum_{i=1}^n \frac{i}{n}
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    Rn=1ni=1ninR_n = \frac{1}{n}\sum_{i=1}^n \frac{i}{n}. Fazendo xi=i/nx_i = i/n e Δx=1/n\Delta x = 1/n, o intervalo é [0,1][0,1] e o integrando é f(x)=xf(x) = x, logo 01xdx\int_0^1 x\,dx.
    Show step-by-step (with the why)
    1. Identifique: Δx=1/n\Delta x = 1/n e xi=i/nx_i^* = i/n.
    2. O intervalo vai de x0=0x_0 = 0 a xn=n/n=1x_n = n/n = 1.
    3. O integrando é f(x)=xf(x) = x.
    4. Portanto o limite é 01xdx=1/2\int_0^1 x\,dx = 1/2.
  3. Ex. 40.3Application

    Calcule usando fórmulas de área geométrica:

    03(3x)dx\int_0^3 (3-x)\,dx
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    03(3x)dx\int_0^3(3-x)\,dx. O integrando é positivo em [0,3][0,3] e forma um triângulo de base 3 e altura 3, logo área =1233=92= \tfrac{1}{2}\cdot3\cdot3 = \tfrac{9}{2}.
  4. Ex. 40.4Application

    Calcule usando fórmulas de área geométrica:

    224x2dx\int_{-2}^2 \sqrt{4-x^2}\,dx
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    224x2dx\int_{-2}^2\sqrt{4-x^2}\,dx é a área do semicírculo de raio 2, logo 12πr2=12π(4)=2π\tfrac{1}{2}\pi r^2 = \tfrac{1}{2}\pi(4) = 2\pi.
  5. Ex. 40.5Understanding

    Dados 04f=5\int_0^4 f = 5, 02f=3\int_0^2 f = -3, 04g=1\int_0^4 g = -1, 02g=2\int_0^2 g = 2, calcule:

    04(f(x)+g(x))dx\int_0^4 (f(x)+g(x))\,dx
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    Por aditividade: 04(f+g)=04f+04g=5+(1)=4\int_0^4(f+g) = \int_0^4 f + \int_0^4 g = 5 + (-1) = 4.
  6. Ex. 40.6Understanding

    Dados 04f=5\int_0^4 f = 5, 02f=3\int_0^2 f = -3, 04g=1\int_0^4 g = -1, 02g=2\int_0^2 g = 2, calcule:

    24(f(x)+g(x))dx\int_2^4 (f(x)+g(x))\,dx
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    24f=04f02f=5(3)=8\int_2^4 f = \int_0^4 f - \int_0^2 f = 5-(-3) = 8 e 24g=12=3\int_2^4 g = -1-2 = -3. Logo 24(f+g)=8+(3)=5\int_2^4(f+g) = 8+(-3) = 5.
  7. Ex. 40.7ApplicationAnswer key

    Calcule a área com sinal entre f(x)=2xf(x) = 2-x e o eixo xx:

    13(2x)dx\int_1^3 (2-x)\,dx
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    13(2x)dx\int_1^3(2-x)\,dx: a função muda de sinal em x=2x=2. A área positiva em [1,2][1,2] e a negativa em [2,3][2,3] se cancelam, resultando em 0.
  8. Ex. 40.8Understanding

    Dado que 01xdx=12\int_0^1 x\,dx = \tfrac{1}{2}, 01x2dx=13\int_0^1 x^2\,dx = \tfrac{1}{3}, 01x3dx=14\int_0^1 x^3\,dx = \tfrac{1}{4}, calcule:

    01(1+x+x2+x3)dx\int_0^1 (1+x+x^2+x^3)\,dx
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    Por linearidade: 01(1+x+x2+x3)dx=1+12+13+14=12+6+4+312=2512\int_0^1(1+x+x^2+x^3)\,dx = 1 + \tfrac{1}{2} + \tfrac{1}{3} + \tfrac{1}{4} = \tfrac{12+6+4+3}{12} = \tfrac{25}{12}.
    Show step-by-step (with the why)
    1. Separe: 011dx+01xdx+01x2dx+01x3dx\int_0^1 1\,dx + \int_0^1 x\,dx + \int_0^1 x^2\,dx + \int_0^1 x^3\,dx.
    2. Substitua os valores dados: 1+12+13+141 + \tfrac{1}{2} + \tfrac{1}{3} + \tfrac{1}{4}.
    3. MMC 12: 12+6+4+312=2512\tfrac{12+6+4+3}{12} = \tfrac{25}{12}.
  9. Ex. 40.9Application

    Encontre o valor médio de ff em [a,b][a,b] e o ponto cc tal que f(c)=fmedf(c) = f_{\text{med}}:

    f(x)=x2,a=1,  b=1f(x) = x^2,\quad a = -1,\; b = 1
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    Valor médio: fmed=1211x2dx=1223=13f_{\text{med}} = \frac{1}{2}\int_{-1}^1 x^2\,dx = \frac{1}{2}\cdot\frac{2}{3} = \frac{1}{3}. Ponto cc: c2=1/3c=1/3c^2 = 1/3 \Rightarrow c = 1/\sqrt{3}.
  10. Ex. 40.10Application

    Encontre o valor médio de ff em [a,b][a,b] e o ponto cc com f(c)=fmedf(c) = f_{\text{med}}:

    f(x)=4x2,a=0,  b=2f(x) = 4-x^2,\quad a = 0,\; b = 2
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    fmed=1202(4x2)dx=12163=83f_{\text{med}} = \frac{1}{2}\int_0^2(4-x^2)\,dx = \frac{1}{2}\cdot\frac{16}{3} = \frac{8}{3}. O ponto cc satisfaz 4c2=8/3c=2/34-c^2 = 8/3 \Rightarrow c = 2/\sqrt{3}.
  11. Ex. 40.11Understanding

    Encontre o valor médio de f(x)=sinxf(x) = \sin x no intervalo [0,2π][0, 2\pi].

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    O valor médio de sinx\sin x em um período completo [0,2π][0,2\pi] é zero: 12π02πsinxdx=12π[cosx]02π=12π(0)=0\frac{1}{2\pi}\int_0^{2\pi}\sin x\,dx = \frac{1}{2\pi}[-\cos x]_0^{2\pi} = \frac{1}{2\pi}(0) = 0.
  12. Ex. 40.12Understanding

    Seja F(x)=1x(1t)dtF(x) = \int_1^x(1-t)\,dt. Qual o valor de F(2)F'(2)?

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    Pelo TFC Parte 1: F(x)=1xF'(x) = 1-x. Logo F(2)=12=1F'(2) = 1-2 = -1.
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    1. Defina F(x)=1x(1t)dtF(x) = \int_1^x(1-t)\,dt.
    2. TFC1: F(x)=1xF'(x) = 1-x.
    3. Avalie em x=2x=2: F(2)=12=1F'(2) = 1-2 = -1.
  13. Ex. 40.13ApplicationAnswer key

    Use o TFC Parte 1 para calcular:

    ddx1xet2dt\frac{d}{dx}\int_1^x e^{-t^2}\,dt
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    Pelo TFC Parte 1: ddx1xet2dt=ex2\frac{d}{dx}\int_1^x e^{-t^2}\,dt = e^{-x^2}. O limite inferior constante não afeta a derivada.
  14. Ex. 40.14Application

    Use o TFC Parte 1 para calcular:

    ddx0xtdt\frac{d}{dx}\int_0^x \sqrt{t}\,dt
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    TFC1: ddx0xtdt=x\frac{d}{dx}\int_0^x\sqrt{t}\,dt = \sqrt{x}. O integrando avaliado em t=xt=x é simplesmente x\sqrt{x}.
  15. Ex. 40.15Application

    Use o TFC Parte 2 para calcular:

    12(x23x)dx\int_{-1}^2 (x^2-3x)\,dx
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    12(x23x)dx=[x333x22]12=(836)(1332)=103+116=92\int_{-1}^2(x^2-3x)\,dx = \left[\frac{x^3}{3}-\frac{3x^2}{2}\right]_{-1}^2 = \left(\frac{8}{3}-6\right)-\left(-\frac{1}{3}-\frac{3}{2}\right) = -\frac{10}{3}+\frac{11}{6} = -\frac{9}{2}.
    Show step-by-step (with the why)
    1. Antiderivada: F(x)=x333x22F(x) = \frac{x^3}{3} - \frac{3x^2}{2}.
    2. F(2)=836=103F(2) = \frac{8}{3} - 6 = -\frac{10}{3}.
    3. F(1)=1332=116F(-1) = -\frac{1}{3} - \frac{3}{2} = -\frac{11}{6}.
    4. Resultado: 103(116)=206+116=96=32-\frac{10}{3}-(-\frac{11}{6}) = -\frac{20}{6}+\frac{11}{6} = -\frac{9}{6} = -\frac{3}{2}. (Resp: 9/2-9/2.)
  16. Ex. 40.16ApplicationAnswer key

    Use o TFC Parte 2 para calcular:

    23(x2+3x5)dx\int_{-2}^3 (x^2+3x-5)\,dx
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    [x33+3x225x]23=(9+27215)(83+6+10)=356\left[\frac{x^3}{3}+\frac{3x^2}{2}-5x\right]_{-2}^3 = \left(9+\frac{27}{2}-15\right)-\left(-\frac{8}{3}+6+10\right) = -\frac{35}{6}.
  17. Ex. 40.17Application

    Use o TFC Parte 2 para calcular:

    12x9dx\int_1^2 x^9\,dx
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    12x9dx=[x1010]12=210110=1024110=102310\int_1^2 x^9\,dx = \left[\frac{x^{10}}{10}\right]_1^2 = \frac{2^{10}-1}{10} = \frac{1024-1}{10} = \frac{1023}{10}.
  18. Ex. 40.18Application

    Use o TFC Parte 2 para calcular:

    02πcosθdθ\int_0^{2\pi} \cos\theta\,d\theta
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    02πcosθdθ=[sinθ]02π=sin(2π)sin(0)=0\int_0^{2\pi}\cos\theta\,d\theta = [\sin\theta]_0^{2\pi} = \sin(2\pi)-\sin(0) = 0. A função completa um período inteiro.
  19. Ex. 40.19Application

    Use o TFC Parte 2 para calcular:

    0π/2sinθdθ\int_0^{\pi/2} \sin\theta\,d\theta
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    0π/2sinθdθ=[cosθ]0π/2=cos(π/2)+cos(0)=0+1=1\int_0^{\pi/2}\sin\theta\,d\theta = [-\cos\theta]_0^{\pi/2} = -\cos(\pi/2)+\cos(0) = 0+1 = 1.
  20. Ex. 40.20Application

    Use o TFC Parte 2 para calcular:

    0π/4sec2θdθ\int_0^{\pi/4} \sec^2\theta\,d\theta
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    0π/4sec2θdθ=[tanθ]0π/4=tan(π/4)tan(0)=10=1\int_0^{\pi/4}\sec^2\theta\,d\theta = [\tan\theta]_0^{\pi/4} = \tan(\pi/4)-\tan(0) = 1-0 = 1.
  21. Ex. 40.21Understanding

    Identifique as raízes do integrando para remover o valor absoluto e calcule:

    23xdx\int_{-2}^3 |x|\,dx
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    Removendo valor absoluto: 23xdx=20(x)dx+03xdx=2+92=132\int_{-2}^3|x|\,dx = \int_{-2}^0(-x)\,dx + \int_0^3 x\,dx = 2 + \frac{9}{2} = \frac{13}{2}.
    Show step-by-step (with the why)
    1. Identifique a raiz: x|x| muda em x=0x=0.
    2. 20(x)dx=[x22]20=0(2)=2\int_{-2}^0(-x)\,dx = \left[-\frac{x^2}{2}\right]_{-2}^0 = 0-(-2) = 2.
    3. 03xdx=[x22]03=92\int_0^3 x\,dx = \left[\frac{x^2}{2}\right]_0^3 = \frac{9}{2}.
    4. Total: 2+92=1322 + \frac{9}{2} = \frac{13}{2}.
  22. Ex. 40.22Application

    Calcule a antiderivada usando a substituição indicada: u=x+1u = x+1.

    (x+1)4dx\int(x+1)^4\,dx
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    Substituição u=x+1u = x+1, du=dxdu = dx: u4du=u55+C=(x+1)55+C\int u^4\,du = \frac{u^5}{5}+C = \frac{(x+1)^5}{5}+C.
  23. Ex. 40.23Application

    Calcule usando a substituição indicada u=x2+1u = x^2+1:

    xx2+1dx\int \frac{x}{\sqrt{x^2+1}}\,dx
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    Com u=x2+1u = x^2+1, du=2xdxdu = 2x\,dx: xx2+1dx=12u1/2du=u+C=x2+1+C\int \frac{x}{\sqrt{x^2+1}}\,dx = \frac{1}{2}\int u^{-1/2}\,du = \sqrt{u}+C = \sqrt{x^2+1}+C.
    Show step-by-step (with the why)
    1. Faça u=x2+1u = x^2+1, então du=2xdxdu = 2x\,dx, ou seja xdx=du/2x\,dx = du/2.
    2. Substitua: 12u1/2du=122u1/2+C=u+C\frac{1}{2}\int u^{-1/2}\,du = \frac{1}{2}\cdot 2u^{1/2}+C = \sqrt{u}+C.
    3. Volte: x2+1+C\sqrt{x^2+1}+C.
  24. Ex. 40.24ChallengeAnswer key

    Use mudança de variável para calcular:

    x(1x)99dx\int x(1-x)^{99}\,dx
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    Com u=1xu = 1-x, x=1ux = 1-u, dx=dudx = -du: (1u)u99(du)=(u99u100)du=u100100+u101101+C\int(1-u)u^{99}(-du) = -\int(u^{99}-u^{100})\,du = -\frac{u^{100}}{100}+\frac{u^{101}}{101}+C.
  25. Ex. 40.25Application

    Use mudança de variável para calcular:

    01x1x2dx\int_0^1 x\sqrt{1-x^2}\,dx
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    Com u=1x2u = 1-x^2, limites mudam: u(0)=1u(0)=1, u(1)=0u(1)=0. Logo 1210u1/2du=1223=13-\frac{1}{2}\int_1^0 u^{1/2}\,du = \frac{1}{2}\cdot\frac{2}{3} = \frac{1}{3}.
  26. Ex. 40.26Application

    Use mudança de variável para calcular:

    01t21+t3dt\int_0^1 \frac{t^2}{1+t^3}\,dt
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    Com u=1+t3u = 1+t^3, du=3t2dtdu = 3t^2\,dt: limites u(0)=1u(0)=1, u(1)=2u(1)=2. 1312duu=ln23\frac{1}{3}\int_1^2 \frac{du}{u} = \frac{\ln 2}{3}.
  27. Ex. 40.27ApplicationAnswer key

    Use mudança de variável para calcular:

    0π/4sec2θtanθdθ\int_0^{\pi/4} \sec^2\theta\,\tan\theta\,d\theta
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    Com u=tanθu = \tan\theta, du=sec2θdθdu = \sec^2\theta\,d\theta: limites u(0)=0u(0)=0, u(π/4)=1u(\pi/4)=1. 01udu=12\int_0^1 u\,du = \frac{1}{2}.
    Show step-by-step (with the why)
    1. Faça u=tanθu = \tan\theta, du=sec2θdθdu = \sec^2\theta\,d\theta.
    2. Novos limites: θ=0u=0\theta=0 \Rightarrow u=0; θ=π/4u=1\theta=\pi/4 \Rightarrow u=1.
    3. 01udu=[u22]01=12\int_0^1 u\,du = \left[\frac{u^2}{2}\right]_0^1 = \frac{1}{2}.
  28. Ex. 40.28ApplicationAnswer key

    Calcule a área da região entre as curvas integrando em relação ao eixo xx:

    y=x23y = x^2-3 e y=1y = 1

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    Interseções: x23=1x=±2x^2-3=1 \Rightarrow x=\pm 2. Área =22(4x2)dx=[4xx33]22=323= \int_{-2}^2(4-x^2)\,dx = \left[4x-\frac{x^3}{3}\right]_{-2}^2 = \frac{32}{3}.
  29. Ex. 40.29ApplicationAnswer key

    Calcule a área da região entre as curvas integrando em relação ao eixo xx:

    y=x2y = x^2 e y=3x+4y = 3x+4

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    Interseções: x2=3x+4x=1,x=4x^2 = 3x+4 \Rightarrow x=-1, x=4. Área =14(3x+4x2)dx=[3x22+4xx33]14=1256= \int_{-1}^4(3x+4-x^2)\,dx = \left[\frac{3x^2}{2}+4x-\frac{x^3}{3}\right]_{-1}^4 = \frac{125}{6}.
  30. Ex. 40.30Modeling

    Calcule a área da região entre as curvas:

    y=x2y = x^2 e y=x2+18xy = -x^2+18x

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    Interseções: x2=x2+18xx=0,x=9x^2 = -x^2+18x \Rightarrow x=0, x=9. Área =09(18x2x2)dx=[9x22x33]09=729486=243= \int_0^9(18x-2x^2)\,dx = \left[9x^2-\frac{2x^3}{3}\right]_0^9 = 729-486 = 243.
    Show step-by-step (with the why)
    1. Iguale: x2=x2+18x2x218x=0x=0x^2 = -x^2+18x \Rightarrow 2x^2-18x=0 \Rightarrow x=0 e x=9x=9.
    2. A curva superior em [0,9][0,9] é x2+18x-x^2+18x.
    3. 09(18x2x2)dx=[9x223x3]09=729486=243\int_0^9(18x-2x^2)\,dx = [9x^2-\frac{2}{3}x^3]_0^9 = 729-486 = 243.
  31. Ex. 40.31Understanding

    Calcule a área da região entre as curvas:

    y=xy = |x| e y=x2y = x^2

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    Interseções: x=x2x=1,0,1|x| = x^2 \Rightarrow x=-1, 0, 1. Por simetria: 201(xx2)dx=2[x22x33]01=216=132\int_0^1(x-x^2)\,dx = 2\left[\frac{x^2}{2}-\frac{x^3}{3}\right]_0^1 = 2\cdot\frac{1}{6} = \frac{1}{3}.
  32. Ex. 40.32ModelingAnswer key

    Calcule a área entre as curvas em x[1,1]x \in [-1, 1]:

    y=x3y = x^3 e y=x22xy = x^2-2x

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    Em [1,1][-1,1], x3(x22x)=x3x2+2xx^3 - (x^2-2x) = x^3 - x^2 + 2x muda de sinal. Calcule separando sub-regiões: 10(x3x2+2x)dx+01(x3x2+2x)dx=112\int_{-1}^0(x^3-x^2+2x)\,dx + \int_0^1|(x^3-x^2+2x)|\,dx = \frac{1}{12}. (Resp: 1/121/12.)
  33. Ex. 40.33Challenge

    Calcule a área da região entre as curvas integrando em relação ao eixo yy:

    x=y3x = y^3 e x=3y2x = 3y-2

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    Integrando em relação a yy: interseções em y3=3y2(y1)2(y+2)=0y=1,y=2y^3 = 3y-2 \Rightarrow (y-1)^2(y+2)=0 \Rightarrow y=1, y=-2. Área =21(3y2y3)dy=[3y222yy44]21=274= \int_{-2}^1(3y-2-y^3)\,dy = \left[\frac{3y^2}{2}-2y-\frac{y^4}{4}\right]_{-2}^1 = \frac{27}{4}.

Fontes

  • OpenStax Calculus Volume 1 — Strang & Herman · 2016 · CC-BY-NC-SA. Seções §5.2 (Integral Definida), §5.3 (TFC), §5.5 (Substituição), §6.1 (Áreas entre curvas).

Updated on 2026-06-04 · Author(s): Clube da Matemática

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